After Wednesday night’s smashing debate victory for Romney, we may expect the national and swing state polls to change in the Republican’s direction. But not by as much as they should. These polls are biased in favor of Obama and here’s the data to prove it:

From noted Republican pollster John McLaughlin comes a clear and convincing exposé of the bias of media polls in the swing states of Florida, Ohio, and Virginia.

McLaughlin reviewed exit polls in each state for the past four elections. From this data about who actually voted, he found that the party divisions manifest on election day have little to do with the samples upon which the media is basing its polling. And, coincidentally, it is always the Republican vote that tends to be undercounted.

In Florida, for example, McLaughlin finds that the average of the last four elections produced a turnout of 37% Democrats and 38% Republicans. But here is the partisan distribution of the most recent Florida media polls:

9-26: CBS/NY Times = 36% Dem / 27% Rep

9-23: Wash Post = 35% Dem / 29% Rep

So the media polls reflect a 9 point and six point Democratic edge even though the actual experience of the past four elections has been a 1 point Republican advantage.

Things are no better in Ohio. Here, McLaughlin finds a 2 point Democratic edge in the past four elections (38% Dem, 36% Rep). But the media polls show vastly more Democrats and fewer Republicans in their samples:

9-26: CBS/NY Times = 35% Dem / 26% Rep

9-23: Wash Post = 35% Dem / 27% Rep

9-11: NBC/Wall St Journal = 38% Dem / 28% Rep

Once again, the actual exit poll-measured vote in Ohio shows a 2 point Democratic edge, but the polls reflect Democratic advantages of 9 points, 8 points, and 10 points respectively.

In Virginia, it’s the same story. The last four elections have a combined 1 point Republican edge, 37-36. But the media polls show a big pro-Democratic bias:

10/2: Roanoke College = Democrat 36% / Republican 27%

9/17: CBS/NYTimes = Democrat 35% / Republican 26%

9/16: Washington Post = Democrat 35% / Republican 24%

9/11: NBC/Wall St Journal = Democrat 31% / Republican 26%

So instead of showing a 1 point Republican edge, these media poll samples show Democratic advantages of 9,9,11, and 5.

The correct conclusion to draw from all these polls is that Romney is comfortably ahead in Virginia and Florida while he holds a slight lead in Ohio. And, remember these polls are all pre-debate!

Also, bear in mind that the undecided vote in all of these polls usually goes against the incumbent.